This application claims the benefit of Korean Patent Application No. 1999-0050513, filed on Nov. 15, 1999, under 35 U.S.C. xc2xa7 119, the entirety of which is hereby incorporated by reference.
1. Field of the invention
The present invention relates to a liquid crystal display device, and more particularly, to an array substrate having color filters for use in a liquid crystal display (LCD) device and a method of manufacturing the same.
2. Description of Related Art
A typical LCD device includes upper and lower substrates with a liquid crystal layer interposed therebetween. The upper substrate includes a color filter and a common electrode. The lower substrate includes a switching element and a pixel electrode and is called an array substrate. The lower and upper substrates are assembled after being formed separately. During the forming processes the upper substrate experiences some heating treatment such as pre-bake, exposure to light, post-bake and so on, mainly for formation of color filters, which may result in deformation of the elements of the upper substrate, which causes misalignment for assembling of the lower and upper substrates.
In this aspect, the lower substrate or array substrate having color filters is suggested. FIG. 1 is a plan view of the conventional array substrate having color filters. On the substrate 11, gate and data lines 13 and 15 cross each other in the matrix and the near the cross points there are formed thin film transistors xe2x80x9cTxe2x80x9d, each of which is comprised of a gate electrode 17 which is a portion of the gate line 13, an active layer 19, a source electrode 21, and a drain electrode 23. For the simplicity, there is shown only one transistor xe2x80x9cTxe2x80x9d.
A pixel electrode 25, which is connected to the drain electrode 23 via a contact hole 27, is formed in a pixel region defined by the gate and data lines 13 and 15.
Under the pixel electrode 25 is positioned a color filter 29 which partially overlaps the gate and data lines 13 and 15. A black matrix 31 is formed along the gate line 13 covering the thin film transistor in order to prevent light from entering the active layer 19.
FIGS. 2a to 2e are cross sectional views taken along line IIxe2x80x94II of FIG. 1 showing a fabricating process.
As shown in FIG. 2a, on the substrate 11 a gate line 13 having gate electrode 17 is formed and the gate insulating layer 18 is formed on the gate line 13. On the gate insulating layer 18 over the gate electrode 17 an active layer 19 is formed, and at the end portions of the active layer 19 the source and drain electrodes 21 and 23 are formed, which defines an intermediate structure. The source electrode 21 is elongated from the data line 15. Next, a first protecting layer 20 of insulating material is formed over the intermediate structure.
And then, as shown in FIG. 2b, a color filter layer 29 is formed on a pixel region defined by the gate and data lines 13 and 15. The color of the filter layer is one of green (G), red (R) or blue (B) and overlaps the gate and data lines 13 and 15 except over the active layer 19 and a portion 27 over the drain electrode 23.
Next, a black matrix 31 is formed over the active layer 19. Chrome, CR, is generally used for the black matrix 31, since it has a low value of light reflection.
Next, a second protecting layer 33 of benzocyclobutene (BCB) is formed and a drain contact hole corresponding to the portion 27 is formed by etching the first and second protecting layers 20 and 33.
Next, as shown in FIG. 2e, a pixel electrode 25 of transparent conductive material is formed while being connected to the drain electrode 23 through the contact hole 27.
The color filter layer can be formed in the array substrate by the process explained above, and misalignment can be reduced. However, in this type of array substrate, two protecting layers 20 and 33 are necessary, which requires more complicated processing.
It should be noted that the parasite capacitance between the pixel electrode 25 and the data line 15, which causes cross talk, is required to be reduced.
To overcome the problems described above, embodiments of the present invention provide array substrates (and methods of making the same) for use in a liquid crystal display device, which have a structure that can simplify the manufacturing process and reduce the parasitic capacity between the pixel electrode and the data line.
Advantages of the present invention will become more apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
In an aspect of the invention, the present invention provides a method of fabricating an array substrate (as well as the array substrate itself), the method including: forming a gate line having a gate electrode on a substrate; forming a color filter layer on the substrate, the color filter layer spaced apart from the gate line; forming a first insulating layer on the color filter layer and the gate line; forming a semiconductor layer and ohmic contact layer sequentially on the gate electrode; forming a data line crossing the gate line; forming source and drain electrodes on the ohmic contact layer; wherein the formation of the data line and the source and drain electrodes completes an intermediate structure; forming a protecting layer of transparent insulating material on the intermediate structure, the protecting layer having a drain contact hole at a corresponding position of the drain electrode; and forming a pixel electrode on the protecting layer that contacts the drain electrode through the drain contact hole. Such an array substrate eliminates a need for separate or discrete black matrix elements because the arrangement permits the gate and data lines to also perform the light blocking function of the black matrix.
In an another aspect of the invention, the present invention provides a method of fabricating an array substrate (as well as the substrate itself) for an LCD device, the method including: forming a light shielding layer having a shape of an island on a substrate; forming a buffer layer on the substrate and the light shielding layer; forming an active layer on the buffer layer over the light shielding layer, the active layer having an island shape; forming a first insulating layer on the active layer and the buffer layer; forming a gate electrode on the first insulating layer; forming a color filter spaced apart from the gate electrode on the same plane as the gate electrode to complete an intermediate structure; forming a gate insulating layer of transparent insulating material on the intermediate structure, the gate insulating layer having first and second contact holes; forming the source and drain electrodes on the protecting layer, the source and drain electrodes connecting to the active layer via the first and second contact holes, respectively; forming a protecting layer of transparent insulating material on the source and drain electrodes, the protecting layer having a drain contact hole exposing the drain electrode; forming a pixel electrode on the protecting layer, the pixel electrode connecting to the drain electrode through the drain contact hole.
In an another aspect of the invention, the invention provides a method for fabricating an array substrate (as well as the array substrate itself), for an LCD device, the method including: forming a light shielding layer on a substrate; forming a first insulating layer on the light shielding layer; forming an active layer on the first insulating layer; forming a second insulating layer on the active layer; forming a gate electrode on the second insulating layer; forming a third insulating layer on the gate electrode; forming source and drain electrodes on the third insulating layer, the source and drain electrodes connecting to the active layer; forming a color filter layer on the third insulating layer; forming a fourth insulating layer of transparent material on the source and drain electrodes and the color filter layer; and forming a pixel electrode on the fourth insulating layer, the pixel electrode contacting the drain electrode.